193 research outputs found
Fixing the U-band photometry of Type Ia supernovae
We present previously unpublished photometry of supernovae 2003gs and 2003hv.
Using spectroscopically-derived corrections to the U-band photometry, we
reconcile U-band light curves made from imagery with the Cerro Tololo 0.9-m,
1.3-m and Las Campanas 1-m telescopes. Previously, such light curves showed a
0.4 mag spread at one month after maximum light. This gives us hope that a set
of corrected ultraviolet light curves of nearby objects can contribute to the
full utilization of rest frame U-band data of supernovae at redshift ~0.3 to
0.8. As pointed out recently by Kessler et al. in the context of the Sloan
Digital Sky Survey supernova search, if we take the published U-band photometry
of nearby Type Ia supernovae at face value, there is a 0.12 mag U-band anomaly
in the distance moduli of higher redshift objects. This anomaly led the Sloan
survey to eliminate from their analyses all photometry obtained in the rest
frame U-band. The Supernova Legacy Survey eliminated observer frame U-band
photometry, which is to say nearby objects observed in the U-band, but they
used photometry of high redshift objects no matter in which band the photons
were emitted.Comment: 25 pages, 9 figures, accepted for publication in the Astronomical
Journa
Hubble Diagrams of Type Ia Supernovae in the Near Infrared
From observations of 7 Type Ia supernovae obtained during the last four years
at the Las Campanas and Cerro Tololo Inter-American Observatories, along with
previous published data for 9 supernovae, we present JHK Hubble diagrams and
derive absolute magnitudes at maximum light of 16 objects out to a redshift of
0.038. On the scale of H_0 = 72 km/s/Mpc we find mean absolute magnitudes at
maximum of -18.57, -18.24, and -18.42 for J, H, and K, respectively, with
1-sigma uncertainties of the distributions of values of +/- 0.14, 0.18, and
0.12 mag. The data indicate no significant decline rate relations for the
infrared. Thus, Type Ia SNe at maximum brightness appear to be standard candles
in the infrared at the +/- 0.20 mag level or better. The minimum requirements
for obtaining the distance to a Type Ia SN are: reasonably accurate values of
Delta m_15(B) and T(B_max), and one night of infrared data in the -12 to +10 d
window with respect to T(B_max).Comment: 15 pages, 3 figures, published in the Astrophysical Journal, vol.
602, pp. L81-L84 (20 February 2004). This version gives more credit where
credit is du
Maximum Brightness and Post-Maximum Decline of Light Curves of SN~Ia: A Comparison of Theory and Observations
We compare the observed correlations between the maximum brightness,
postmaximum decline rate and color at maximum light of Type Ia supernovae (SN
Ia) with model predictions.
The observations are based on a total of 40 SN Ia with 29 SN of the Calan
Tololo Supernova Search and 11 local SN which cover a range of 2 mag in the
absolute visual brightness.
The observed correlations are not tight, one dimensional relations.
Supernovae with the same postmaximum decline or the same color have a spread in
visual magnitude of about 0.7 mag. The dispersion in the color-magnitude
relation may result from uncertainties in the distance determinations or the
interstellar reddening within the host galaxy. The dispersion in the decline
rate-magnitude relation suggests that an intrinsic spread in the supernova
properties exists that cannot be accounted for by any single relation between
visual brightness and postmaximum decline.
Theoretical correlations are derived from a grid of models which encompasses
delayed detonations, pulsating delayed detonations, the merging scenario and
helium detonations.
We find that the observed correlations can be understood in terms of
explosions of Chandrasekhar mass white dwarfs.
Our models show an intrinsic spread in the relations of about 0.5 mag in the
maximum brightness and about 0.1 mag in the B-V color.
Our study provides strong evidence against the mechanism of helium detonation
for subluminous, red SN Ia.Comment: 7 pages, 3 figures, macros ''aaspp.sty'. LaTeX Style. Astrophysical
Journal Letters, submitted Jul. 1995, revised Aug. 1995, resubmitted Sep.
199
The Carnegie Supernova Project I: methods to estimate host-galaxy reddening of stripped-envelope supernovae
We aim to improve upon contemporary methods to estimate host-galaxy reddening
of stripped-envelope (SE) supernovae (SNe). To this end the Carnegie Supernova
Project (CSP-I) SE SNe photometry data release, consisting of nearly three
dozen objects, is used to identify a minimally reddened sub-sample for each
traditionally defined spectroscopic sub-types (i.e, SNe~IIb, SNe~Ib, SNe~Ic).
Inspection of the optical and near-infrared (NIR) colors and color evolution of
the minimally reddened sub-samples reveals a high degree of homogeneity,
particularly between 0d to +20d relative to B-band maximum. This motivated the
construction of intrinsic color-curve templates, which when compared to the
colors of reddened SE SNe, yields an entire suite of optical and NIR color
excess measurements. Comparison of optical/optical vs. optical/NIR color excess
measurements indicates the majority of the CSP-I SE SNe suffer relatively low
amounts of reddening and we find evidence for different R_(V)^(host) values
among different SE SN. Fitting the color excess measurements of the seven most
reddened objects with the Fitzpatrick (1999) reddening law model provides
robust estimates of the host visual-extinction A_(V)^(host) and R_(V)^(host).
In the case of the SE SNe with relatively low amounts of reddening, a preferred
value of R_(V)^(host) is adopted for each sub-type, resulting in estimates of
A_(V)^(host) through Fitzpatrick (1999) reddening law model fits to the
observed color excess measurements. Our analysis suggests SE SNe reside in
galaxies characterized by a range of dust properties. We also find evidence SNe
Ic are more likely to occur in regions characterized by larger R_(V)^(host)
values compared to SNe IIb/Ib and they also tend to suffer more extinction.
These findings are consistent with work in the literature suggesting SNe Ic
tend to occur in regions of on-going star formation.Comment: Abstract abridged to fit allowed limit. Resubmitted to A&A, 34 pages,
19 figures, 6 tables. Constructive comments welcome
The Reddening-Free Decline Rate Versus Luminosity Relationship for Type Ia Supernovae
We develop a method for estimating the host galaxy dust extinction for type
Ia supernovae based on an observational coincidence first noted by Lira (1995),
who found that the B-V evolution during the period from 30-90 days after V
maximum is remarkably similar for all events, regardless of light curve shape.
This fact is used to calibrate the dependence of the B(max)-V(max) and
V(max)-I(max) colors on the light curve decline rate parameter delta-m15, which
can, in turn, be used to separately estimate the host galaxy extinction. Using
these methods to eliminate the effects of reddening, we reexamine the
functional form of the decline rate versus luminosity relationship and provide
an updated estimate of the Hubble constant of Ho = 63.3 +- 2.2(internal) +-
3.5(external) km/s/Mpc.Comment: 32 pages, 10 figures, AJ 1999 in pres
The Earliest Near-infrared Time-series Spectroscopy of a Type Ia Supernova
We present ten medium-resolution, high signal-to-noise ratio near-infrared
(NIR) spectra of SN 2011fe from SpeX on the NASA Infrared Telescope Facility
(IRTF) and Gemini Near-Infrared Spectrograph (GNIRS) on Gemini North, obtained
as part of the Carnegie Supernova Project. This data set constitutes the
earliest time-series NIR spectroscopy of a Type Ia supernova (SN Ia), with the
first spectrum obtained at 2.58 days past the explosion and covering -14.6 to
+17.3 days relative to B-band maximum. C I {\lambda}1.0693 {\mu}m is detected
in SN 2011fe with increasing strength up to maximum light. The delay in the
onset of the NIR C I line demonstrates its potential to be an effective tracer
of unprocessed material. For the first time in a SN Ia, the early rapid decline
of the Mg II {\lambda}1.0927 {\mu}m velocity was observed, and the subsequent
velocity is remarkably constant. The Mg II velocity during this constant phase
locates the inner edge of carbon burning and probes the conditions under which
the transition from deflagration to detonation occurs. We show that the Mg II
velocity does not correlate with the optical light-curve decline rate
{\Delta}m15. The prominent break at ~1.5 {\mu}m is the main source of concern
for NIR k-correction calculations. We demonstrate here that the feature has a
uniform time evolution among SNe Ia, with the flux ratio across the break
strongly correlated with {\Delta}m15. The predictability of the strength and
the onset of this feature suggests that the associated k-correction
uncertainties can be minimized with improved spectral templates.Comment: 14 pages, 13 figures, accepted for publication in Ap
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